Switching Power Supply Control Circuit Using Negative Voltage Level Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional control circuits for switching power supplies require a thick-film gate process to achieve the necessary withstand voltage between the gate and source of activation switches, which is costly and complicates the manufacturing process.
Innovation Solution
A control circuit for switching power supplies that uses a PMOSFET with a low-withstand voltage gate and high-withstand voltage drain, along with a negative power supply and a control amplifier, to generate a first activation current and control the voltage of the control power supply, eliminating the need for a thick-film gate process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick-film gate process is used to achieve high withstand voltage between gate and source of activation switches, then the voltage withstand capability is improved, but the manufacturing cost increases and the manufacturing process becomes complex
Solution Approach 1:
The patent divides the voltage withstand requirements into two separate components: the activation switch handles the high voltage stress between drain and source, while the gate only needs to handle low voltage control signals. This segmentation allows each component to be optimized independently, with the switch using thick-film gate process only where necessary and the control circuit using simpler thin-film processes.
Solution Approach 2:
The patent introduces a level shift circuit as an intermediary between the low-voltage control circuit and the high-voltage activation switch. This level shift circuit translates low-voltage control signals into high-voltage drive signals, allowing the control circuit to operate at low voltages with simple thin-film processes while still controlling high-voltage switches that can be manufactured with optimized processes.
2Reliability
If a thick-film gate process is used for activation switches, then the gate-source withstand voltage is improved, but the manufacturing cost increases
Solution Approach 1:
The patent applies the thick-film gate process only locally to the activation switch where high voltage stress occurs between drain and source, while the control circuit and other components use simpler and less expensive thin-film processes. This localized application of the expensive thick-film process minimizes manufacturing costs while still achieving the required voltage withstand capability where it is actually needed.
Solution Approach 2:
The patent segments the power supply circuit into high-voltage sections (activation switch) and low-voltage sections (control circuit), allowing different manufacturing processes to be applied to each segment based on their specific requirements. This segmentation enables cost optimization by applying expensive processes only where necessary.
3Adaptability or versatility
If the control circuit operates at high voltage to control activation switches, then the voltage control capability is improved, but the device complexity increases
Solution Approach 1:
The level shift circuit serves as an intermediary that bridges the low-voltage control domain and the high-voltage power domain. It takes simple low-voltage control signals and automatically converts them to the appropriate high-voltage drive signals, providing voltage control capability without requiring the entire control circuit to operate at high voltage, thus maintaining simplicity.
Solution Approach 2:
The patent replaces what would otherwise require complex high-voltage control circuitry with a simpler low-voltage control circuit combined with a level shift interface. This substitution allows the control circuit to remain simple and low-voltage while still achieving high-voltage control capability through the intermediary level shift mechanism.
Data Source
AI summary
A negative power supply generates a voltage Vm that is negative when a source voltage Vh′ of an activation element is used as a reference. A differential voltage between the above-described voltage Vh′ and the voltage Vm is applied to an activation circuit arranged between the activation element and a control power supply voltage Vcc. The activation circuit is configured to include a current detection resistor, a voltage conversion resister, a current source, a first PMOS switch, a second PMOS switch, and a control amplifier. The control amplifier operates in a voltage range between Vh′ and Vm, and an output of the control amplifier is connected to a gate of the first PMOS switch.